The invention relates to sludge treatment and in particular to sludge treatment methods to produce a composted material for agricultural and other similar uses. Specifically, the invention relates to a controlled sludge treatent method that eliminates objectionable odors and provides a useable composted product.
Sewage sludge accumulates at a rapid rate and in areas of large population the disposal becomes a problem. This is particularly so because the raw sludge from the sewage treatment plants has a distinct objectionable and disagreeable odor. The method of this invention provides a means for handling that sludge, eliminating the objectionable odor, and producing a useable product that makes the method economically feasible.
The method described herein is for an ordinary unit. It is to be understood that the method may be used in structures in a range of sizes to handle a range of volumes, or the method may be used in structures as a plurality of similar sized units to handle the total volume of sludge generated.
In the prior art sludge was disposed of by merely dumping it with a result of complaints about the disagreeable and objectional odor. Also, the raw sludge was not readily suitable for direct application to form land, flower beds, and similar uses in its untreated state.
Field treatment in the prior art has been tried in order to obtain a compost material, but this still had the problem of the disagreeable and objectionable odors.
Some treatment methods tried a digester means in order to capture certain gases that were useable, but this did not fully treat the sludge for agricultural use.
The present method of this invention overcomes the aforementioned problems of the prior art. The present invention thoroughly premixes the sludge with carbonaceous material and conveys it to a silo where it is spread evenly over the interior area in a layering manner by a movable distribution means. A timed interval moves the mixture through the silo in a specified period as more layers are added at the top and an equivalent volume (less the amount consumed in the composting process) is removed from the bottom by movable pick-up means.
The partially treated mixture is then conveyed to a second silo and spread, moved at a timed interval, and removed in a similar manner and packaged or bulkhandled for distribution to the user.
In both silos a forced air system passes air through the mixture mass. In the first silo to promote aerobic bacteria action for the composting and in the second silo to complete the process which eliminates the objectionable odors.
It is, therefore, an object of the invention to provide a controlled sludge composting method which will prepare raw sewage sludge for safe disposal and agricultural type uses.
It is another object of the invention to provide a controlled sludge composting method that removes objectionable disagreeable odors from the sludge in its final composted form.
It is also an object of the invention to provide a controlled sludge composting method that uses carbonaceous material as a mixture with the sludge to obtain a composted product.
It is still another object of the invention to provide a controlled sludge composting method that uses forced air to promote aerobic bacteria action in producing the composted end product.
It is yet another object of the invention to provide a controlled sludge composting method that uses forced air to complete the sludge treatment to eliminate disagreeable objectionable odors.
Further objects and advantages of the invention will become more apparent in the light of the following description of the preferred embodiments.